Method of bleaching



fvmch an Hmm? GR 2,029,985 CUN 0F TEXTILES & Fgg *E L Feb. 4, 1936. J. A. CLARK ET AL 2,029,985

METHOD GF BLEACHING Filed May 5l, 1932 l WIW II www *I INVENTORS JwzzeJAmmf/zf BY Ham/mamy 5x20/225 ATTORNEYS "HUN 0F TEXTILES & FIBtQL-Q,

Patented Feb. 4, 1936 UNITED STATES PATENT OFFICE METHOD OF BLEACHING Inc., Tonawanda, N. Y.

Application May 31, 1932, Serial No. 614,522

2 Claims.

This invention relates to a method of bleaching textile bers and more particularly to a method for continuously bleaching textile iibers with solutions of bleaching compounds and to an apparatus.

In bleaching textile fibers heretofore, particularly those fibers containing relatively large quantities of cellulosic material, it has been found that the ber may be bleached either in the raw state, as for instance loose cotton, as yarn in the form of cotton, hanks, or warp, or in the piece. In general, bleaching of textile fibers, such as cotton, includes three main operations; namely, boiling, chemical treatment, and souring. The use to which the liber is to be employed regulates the extent to which these operations are carried out. Bleaching of yarn or cloth in width has been carried out heretofore in what is generally called a kier in which the goods have been piled or draped, and wherein the goods are subjected to the action of bleaching liquor which is permitted to shower over the goods, fall therethrough and be subsequently recirculated to shower over the goods for a period of time on the order of about two hours. Excess bleaching liquor is removed by thoroughly rinsing the goods with Water and dipping in a souring bath which comprises a diluted acid. The yarn is ready for use after it has been subjected to a rinsing operation subsequent to the souring to remove the acid Which would otherwise cause the yarn to become tender and decrease the strength of the resulting bleached fabric.

We have found that we are able to bleach textile fibers, either in the raw state, as yarn, and

especially when in the form of cloth or goods, in

a much shorter period of tir1e`tlf has been found necessary heretofore. In the broad aspect of the invention, we subject the goods either in Y rope form or in the open width, to the action of the bleaching solution whereby the goods become impregnated or padded with the bleaching solution, and thereafter eliminate substantially all of the bleaching solution from the goods, subjecting the moist goods to a predetermined temperature for a time suicient to induce the degree of bleaching desired or until all of the bleaching material retained in the goods has been decomposed.

Thus, the goods are passed continuously through the bleaching solution at such rate as will permit the saturation or padding of the goods with the bleaching solution. This rate will, of course, depend upon the form in which the goods are passed through the solution, whether in rope form or in open width, and upon the previous history of the goods, the particular kind of fiber, etc.; the goods are thereafter passed through a device which eliminates substantially all of the bleaching solution carried by the cloth, yet leave the cloth in a moist condition.

After the greater portion of the bleaching solution has been removed from the goods, the goods are passed continuously through a reaction chamber where the bleaching takes place. The duration of the time of passage of the goods through the reaction chamber is sufficiently long to permit the desired bleaching action of the bleaching solution upon the goods and to this end, the goods are passed through shutes or other suitable devices continuously and for a time sufcient to eiect the desired degree of bleaching.

We further propose to accelerate the bleaching action by maintaining a predetermined temperature within the reaction chamber, as for instance by means of controlled steam pressure. This steam pressure may be either above, below or at atmospheric pressure, and a temperature corresponding to such steam pressure will obtain in the reaction chamber.

By eliminating substantially all of the excess moisture and bleaching solution from the goods We are able to shorten the time of treatment considerably since the amount of heat necessary to raise the temperature of the bleaching solution on the goods is materially decreased due to the fact that only a small quantity of the solution now remains in the fiber or in the interstices between the fibers. Further, any evaporation of liquid contained in the bleaching solution effectively carries away any layer of nonactive or spent bleaching agent in contact with the goods and permits the formation of a new and chenilcally active layer about the goods which aids in the proper bleaching thereof. After passing through the reaction chamber the goods are suitably rinsed to remove residual chemicals and soluble impurities.

As mentioned herein, the duration of .fthe bleaching treatment will vary with the type of goods and the extent to which the goods are to be bleached, in any case, this time will be materially shorter than that required to bleach the same goods by the intermittent method such as 4 that using an injector kier wherein several hours are consumed in loading or unloading the kier and in circulating the bleaching solutions thereover. Whereas several hours are required to obtain a given desired bleach by use of recirculation in a kier, the same bleached condition of the goods may be obtained in a period of time ranging from about ten to about thirty minutes, depending upon the strength of the bleaching solution and the temperature to which the goods are subjected when working in accordance with the present invention; both higher temperatures and higher concentrations of bleaching agents tend to reduce the time necessary to produce a predetermined bleach in the goods.

The goods are caused to pass from the bleaching or reaction chamber into a rinsing bath to eliminate the last traces of the bleaching solution and to eliminate soluble materials in the fiber as mentioned above. In this process the rinsing time is materially reduced over the rinsing time required when the goods are bleached in a kier; in a kier bleach sediment and impurities from the bath collect and accumulate upon the fabric due to the fact that the solution is recirculated through the kier, and this sediment is, in most cases, washed off only with difculty. Since the cause of the sedimentation, recirculation of the solution, has been eliminated, concentration of the sediment upon any given portion of the fiber or goods does not occur in our process. Further, whatever sediment may collect upon the goods from the bleaching solution is not matted in the goods as is often the case of sedimentation from recirculation processes, but is readily removed and detached from the goods.

The process may be carried out in any suitable form of apparatus although we have found a reaction chamber of the type illustrated in the figure to be suitable for the purpose.

The reaction chamber i@ is provided with water seals l I in which the side edges of the top of the reaction chamber are immersed in order to complete the water seal. The water seal is normally in the form of a trough in which the bleaching solution is stored and through which the goods are passed prior to their entrance into the reaction chamber.

The reaction chamber is constructed of suitable materials and of a suitable type whereby temperatures either above or below that of steam at atmospheric pressure may be maintained. The chamber IE) is therefore provided with suitable inlets i2 through which live steam is injected into the chamber at a given pressure in order to maintain a predetermined temperature within the chamber, The chamber is also provided with a Valved discharge passage through which any condensate may be eliminated and removed from the reaction chamber, as at i3.

A J shute is provided Within the reaction chamber and, in the form shown, is formed from imperforate material, although the shute may be provided with perforations or slots to permit of better circulation oi' the heated atmosphere within the chamber. rFhe shute is also provided with a perforated bottom to permit of the removal of any liquid which might drip upon the shute and run down to the bottom portion thereof, as at Hi.

In the operation of the method and apparatus upon goods on open width, the goods 9 pass through rolls i5 which are sunciently long to receive the entire width of the goods in the open condition, are passed downwardly through a bleaching solution i6 contained within the water seal H surrounding a portion of the reaction chamber, passed upwardly therethrough and between squeeze rolls il of suitable type and composition whereby excess bleaching liquor is eliminated from the goods and drips or passes in the main body of the solution in the water seal. The moist goods pass from the squeeze rolls il to the plaiter-down I8 and is there caused to pass down the J shute in regular layers whereby the goods are retained for a greater length of time in contact with the heated atmosphere so that residual quantity of bleaching liquor retained upon the goods may be evaporated or heated to an elevated temperature and thereby act more vigorously upon matters in the goods for the production of a bleached white fabric.

From the J shute the goods pass under the idler roll i9 placed adjacent the bottom of the shute upwardly over the roll 20 and then pass through a rinse 2l of desirable type, as for instance water, placed in another portion of the water seal Il and separate from the bleaching solution I6 in another portion of the seal. Excess rinse solution is squeezed from the goods by the use of squeeze rolls 22.

Both the rinse solution 2| and the bleaching solution I6 may be circulated in the seal Il in any desired fashion, to continuously provide fresh solution for the action of the goods or may be permitted to remain in the seal until tests thereof show either an undue accumulation of foreign matter in the rinse or a change in the composition or amount of the bleach indicating a removal of these solutions.

The temperatures recommended depend upon the history of the goods to be bleached, but for most purposes temperatures at or above 212 F., obtainable from the use of steam at or above atmospheric pressure, are suitable for bleaching in a minimum time. Thus, we have obtained good bleaching of cotton cloth at 4 ounces of steam pressure in l5 minutes, the pressure being regis/"tailed upon, a suitable gauge 25"'at'tasl`id to chamber lil. www' The bleaching solutions employed in the prescnt improved method comprise solutions of hydrogen peroxide of any suitable strength which are maintained in an alkaline condition by the use of suitable agents such as sodium silicate, soda ash, caustic soda or alkaline phosphate of soda or potash and the like, that is, alkaline agents which facilitate the decomposition of the peroxide and consequent bleaching of the ber. This alkaline peroxide solution may, if desired, be produced from water solutions of peroxide of metals other than hydrogen.

The term goods as used herein refers to yarn as well as cloth and textiles in form of hanks or raw fibers in untwisted and unspun state.

We claim:

1. The method of bleaching cotton goods which comprises wetting the goods with a quantity of a solution of hydrogen peroxide in water suflicient to moisten the goods, and thereafter subjecting the goods to a temperature above the boiling point of the solution in an atmosphere containing steam for a period of time suicient to produce the desired bleaching effect in the goods.

2. The method of bleaching cotton goods which comprises wetting the goods with an aqueous solution of hydrogen peroxide, eliminating the major portion of the solution from the goods but permitting the retention of suilicient quantity of the solution to moisten the bers of the goods, and thereafter subjecting the goods to a temperature above the boiling point of the solution in an atmosphere containing steam for a period of time suicient to produce the desired bleaching effect in the goods.

JAMES ANDREW CLARK. HARRY GREGORY SMOLENS. 

